KR20250123232A - Accessory devices to improve wireless power transfer efficiency - Google Patents

Abstract

An accessory (300) for improving wireless power transfer efficiency in a wireless power transfer system can include a magnetic (e.g., ferrite) core dimensioned and positioned to reduce flux coupling from a power transmitter winding (103) to a friendly metal of a power receiver (104) and/or enhance flux coupling from the power transmitter winding (103) to a power receiver winding (105). The core can define an opening corresponding to an outer dimension (e.g., an outer diameter) of the power receiver winding. The core can further have an outer dimension selected to intercept sufficient flux to reduce flux coupling to the friendly metal of the power receiver, e.g., an outer diameter corresponding to the outer dimension ( e.g. , an outer diameter) of the power transmitter winding. The accessory can be a case for the power receiver device (104), or can be configured to attach to a face of the power transmitter device (102) and can also include one or more alignment fixtures.

Description

Accessory devices to improve wireless power transfer efficiency {ACCESSORY DEVICES TO IMPROVE WIRELESS POWER TRANSFER EFFICIENCY}

An exemplary wireless (inductive) power transfer system is illustrated in FIG. 1. The efficiency of wireless (inductive) power transfer between a wireless power transmitter (PTx) (102) and a wireless power receiver (PRx) (104) depends on the degree of magnetic coupling between each PTx winding (winding (103)) and the PRx winding (winding (105)). The wireless (inductive) power transfer windings can take a variety of forms, including coils wound from suitable wire, such as magnet wire or Litz wire, or traces suitably formed on printed circuit boards (PCBs) or flexible printed circuit boards (flex circuits). These windings can be considered generally circular, but need not be substantially planar. Generally circular means that the winding forms a closed loop, but the shape can be any closed shape, including square, rectangular, circular, oval, polygonal, and other shapes, and sometimes does not always have rounded corners. Additionally, the windings will often have a thickness corresponding to the distance between the outermost turns of the winding and the innermost turns of the winding. For example, a circular winding may have an outer diameter (corresponding to the diameter of the outermost turns) and an inner diameter (corresponding to the diameter of the innermost turns of the winding). Depending on the context, "diameter" as used herein may refer to the outer diameter, the inner diameter, or the average of the two. "Diameter" may also be understood to include similar internal or external dimensions in the case of windings that are not strictly circular in shape, such as the length of a side in the case of a square winding, or the length of the major or minor axis in the case of a rectangular or oval winding.

One factor that can affect the degree of magnetic coupling between the windings is the relative sizes of these windings. If there is a size mismatch between the PTx coil and the PRx coil, the magnetic flux from the PTx winding may couple to metallic structures of the receiving device other than the receiver winding. Such structures may be known or referred to as "friendly metal." This coupling may be undesirable because it wastes energy from the transmitter, resulting in reduced efficiency. In some cases, such undesirable magnetic coupling may also cause one or both of the PTx and PRx devices to misinterpret the amount of wireless power being transmitted, leading to feedback loop difficulties.

An accessory for improving wireless power transfer efficiency in a wireless power transfer system comprising a PTx having a power transmitter (PTx) winding and a PRx having a power receiver (PRx) winding, wherein the PTx winding and the PRx winding are dimensionally mismatched, may include a core formed of a material having selected magnetic properties. The core may be dimensioned and positioned to at least one of reduce flux coupling from the PTx winding to an affinity metal of the PRx and improve flux coupling from the PTx winding to the PRx winding. The core may be a ferrite core. The dimensional mismatch between the PTx winding and the PRx winding may include the PTx winding being larger than the PRx winding. In such a case, the core may define an opening corresponding to an outer dimension of the PRx winding. The core may have an outer dimension selected to intercept sufficient flux to reduce flux coupling of the PRx to the affinity metal. The opening may have an inner diameter corresponding to the outer diameter of the PRx winding. The accessory may be configured in various forms, including a shim configured to be attached to the PTx or PRx by adhesives, magnets, mechanical features, etc. The accessory may also be configured as a case for an electronic device, such as a smartphone or smartwatch.

An accessory may be configured to improve wireless power transfer efficiency between an electronic device and a wireless charger when the wireless charging winding of the electronic device and the wireless charging winding of the wireless charger are dimensionally mismatched. The accessory may include a core formed of a material having selected magnetic properties, the core being dimensioned and positioned to at least one of: reduce flux coupling from the wireless charging winding of the wireless charger to metal of the electronic device; and enhance flux coupling from the wireless charging winding of the wireless charger to the wireless charging winding of the device. The accessory may further include one or more alignment fixtures. The one or more alignment fixtures may be configured to align or secure the accessory with respect to the electronic device. Additionally or alternatively, the one or more alignment fixtures may be configured to align or secure a case with respect to the wireless charger. The alignment fixtures may include one or more magnets. The one or more magnets may form a ring. The core may be a ferrite core. The dimensional mismatch may include the wireless charging winding of the wireless charger being larger than the wireless charging winding of the electronic device. In such a case, the core may define an opening corresponding to the outer dimensions of the wireless charging coil of the electronic device. The core may have an outer dimension selected to intercept sufficient flux to reduce flux coupling to the compatible metal of the electronic device. The opening may have an inner diameter corresponding to the outer diameter of the wireless charging coil of the wireless charger.

A wireless charging accessory device may include means for reducing flux coupling from a wireless power transmitting winding of a wireless power transmitter to a friendly metal of a wireless power receiver or for improving flux coupling from the wireless power transmitting winding to a dimensionally mismatched wireless power receiving winding of the wireless power receiver, and means for aligning the means for reducing flux coupling from the wireless power transmitting winding of the wireless power transmitter to a friendly metal of the wireless power receiver or for improving flux coupling from the wireless power transmitting winding to a wireless power receiving winding of the wireless power receiver relative to at least one of the wireless power receiver or the wireless power transmitter. The means for reducing flux coupling from the wireless power transmitting winding of the wireless power transmitter to a friendly metal of the wireless power receiver or for improving flux coupling from the wireless power transmitting winding to the wireless power receiving winding of the wireless power receiver may be a ferrite core. The dimensional mismatch between the wireless power transmitting winding and the wireless power receiving winding may include the wireless power transmitting winding being larger than the wireless power receiving winding, and the core defining an opening corresponding to the external dimensions of the wireless power receiving winding. The core may have an external dimension selected to intercept sufficient flux to reduce flux coupling to the friendly metal of the wireless power receiver.

An accessory may be configured to be attached to a face of a wireless power transmitter to improve wireless power transfer efficiency between an electronic device and a wireless power transmitter, wherein the wireless charging winding of the electronic device and the wireless charging winding of the wireless power transmitter are dimensionally mismatched. The accessory may include a core formed of a material having selected magnetic properties, the core being dimensioned and positioned to at least one of: reduce flux coupling from the wireless charging winding of the wireless power transmitter to metal of the electronic device; and enhance flux coupling from the wireless charging winding of the wireless power transmitter to the wireless charging winding of the electronic device. The accessory may be configured to be attached to the face of the wireless power transmitter by an adhesive or by other means, such as mechanical fasteners. The core may be a ferrite ring dimensioned to shield metal of the electronic device from flux induced by at least one wireless charging winding of the wireless power transmitter. The ferrite ring may include one or more tabs sized and dimensioned to be positioned proximate one or more wireless charging windings of the wireless power transmitter to provide a desired level of shielding or flux diversion. The core may further include additional ferrite bars sized and dimensioned to be positioned proximate one or more wireless charging windings of the wireless power transmitter to provide a desired level of shielding or flux diversion.

Figure 1 illustrates a wireless power transfer system.
Figures 2a and 2b illustrate a wireless power transfer system illustrating flux coupling in a situation with coils of different sizes.
FIGS. 3A and 3B illustrate a wireless power transfer system with an accessory interposed between the PTx and the PRx to improve wireless power transfer efficiency.
FIGS. 4a and 4b, 5a and 5b, 6a and 6b, and 7a and 7b illustrate respective embodiments of wireless power transfer efficiency enhancing accessories.
Figure 8 illustrates an embodiment of a flux shielding/direction diverting accessory including a ferrite core.
Figure 9 illustrates additional details of the flux shielding/direction accessory of Figure 8.
FIG. 10 illustrates an accessory for improving wireless power transfer efficiency including a segmented ferrite core having a corresponding magnetic ring.

In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of the disclosed concepts. As part of this description, some of the drawings in this disclosure depict structures and devices in block diagram form for simplicity. For clarity, not all features of an actual implementation are depicted in this disclosure. Furthermore, the language used in this disclosure has been selected for readability and instructional purposes, and not to delineate or limit the disclosed subject matter. Rather, the appended claims are intended for that purpose.

Various embodiments of the disclosed concepts are illustrated by way of example, and not limitation, in the accompanying drawings, in which like reference numerals represent similar elements. For simplicity and clarity of illustration, reference numerals have been repeated among different drawings, where appropriate, to indicate corresponding or analogous elements. Additionally, numerous specific details are set forth to provide a thorough understanding of the embodiments described herein. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related functionality being described. References in this disclosure to "one," "an," or "another" embodiment are not necessarily to the same or different embodiments, but rather mean at least one. A given drawing may be used to illustrate features of more than one embodiment or more than one type of the present disclosure, and not all elements in a drawing may be required for a given embodiment or type. When provided in a given drawing, reference numerals refer to the same element throughout several drawings, but may not be repeated in every drawing. The drawings are not drawn to scale unless otherwise indicated, and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.

Figures 2a and 2b illustrate a wireless (inductive) power transmission arrangement that includes a size mismatch between a PTx winding (103) and a PRx winding (105). In the illustrated arrangement, the PTx winding (103) has a larger diameter than the PRx winding (105). In other situations not illustrated, the opposite may also apply. In the side view of Figure 2b, flux lines (202) illustrate exemplary flux paths associated with the drive PTx winding (103) (shown in plan view in Figure 2a) in a counterclockwise direction. As can be seen in Figure 2b, some of the flux lines (202) pass through the PRx winding (105). This portion of the flux may be considered to be effectively coupled to the PRx device. However, some of the flux lines (202) do not pass through the PRx winding (105), but rather reach the metal components of the PRx device (104) indicated by “X” markings in FIG. 2B (i.e., the “affinity metal” described above). As long as some of the magnetic flux from 103 interacts with the affinity metal rather than the PRx winding (105), the magnetic coupling between the PTx and PRx is reduced. This may be due, at least in part, to the different sizes of the respective PTx windings (103) and PRx windings (105).

One way to address this size mismatch and improve the degree of magnetic coupling between the PTx winding (103) and the PRx winding (105) is to provide a flux shielding and/or redirecting accessory between the PTx and PRx. FIG. 3A illustrates a side view of such an arrangement, while FIG. 3B illustrates a plan view of such an arrangement. The flux shielding and/or redirecting accessory may include a core (300) made of a ferrite or other ferromagnetic material having suitable magnetic properties, such as sintered ferrite or nanocrystalline sheets. The core (300) may be dimensioned to shield the affinity metal of the PRx (104) from the flux induced by the PTx winding (104) and/or to effectively redirect some or substantially all of such flux to the PRx winding (105).

In the illustrated example having a relatively larger PTx coil (103) and a relatively smaller PRx coil (105), the ferrite core (300) may be ring-shaped having an inner diameter (ID) that generally corresponds to the inner diameter of the PRx coil and an outer diameter (OD) that is sufficiently large to intercept flux from the PTx coil that would otherwise couple to the affinity metal. By positioning such a core (300) between, generally parallel to, and substantially overlapping and coaxial with the respective windings, magnetic coupling between the windings (103, 105) may be improved, and flux coupling to the affinity metal of the PRx device (104) may be reduced.

A substantially similar solution can also be implemented in the opposite situation, where the PRx coil is larger and the PTx coil turns are smaller. Also, as mentioned above, the shapes of the individual turns and core need not be strictly circular, but can be any closed or substantially closed shape, where the diameters mentioned above can be internal side lengths, major and minor axis lengths, etc. By "substantially closed" shape, we mean that the core can be composed of two or more segments of magnetic material, and the spacing between the segments is relatively small (compared to the core size). Importantly, the core (300) is positioned and dimensioned to reduce unwanted flux coupling from the PTx winding (103) to the compatible metal of the PRx device (104) and/or to enhance flux coupling to the PRx winding (105). Additionally, while the described embodiment features substantially planar coils and core (300), the same principles apply to non-planar windings and non-planar intermediate cores (300). In such embodiments, the intermediate core (300) should be shaped, positioned, and dimensioned to reduce undesirable flux coupling to the so-called "friendly metal" and/or to increase the amount of flux coupled into the PRx winding.

In various other implementations, the core (300) dimensionally conforms to the shape of a PTx coil instead of a PRx coil. For example, placing the phone within the case may align the ferrite core (300) with the power transmitting winding (103) of the charging pad (102) such that the outer diameter of the ferrite core/ring (300) aligns with the diameter of the transmitter winding (103) and the inner diameter of the ferrite core/ring (300) is sized such that the central opening of the structure (300) allows flux to flow into the power receiving window (105) of the phone (104). That is, the inner diameter of the ferrite core/ring (300) is larger than the inner diameter of the power receiving winding (105) of the phone (104). In some cases, the inner diameter of the ferrite core/ring (300) is larger than the inner diameter of the power receiving winding (105) and smaller than the outer diameter.

In various implementations of the PTx devices (102) and PRx devices (104), the intermediate device comprising the core (300) can take various forms. As an example, the PTx (102) can be a charging mat, the PRx (104) can be an electronic device such as a mobile phone, a smart watch, a tablet computer, a wireless earphone charging case, or other device, and the intermediate device comprising the ferrite core (300) can be an accessory (400) for the electronic device, as illustrated in FIGS. 4A (top view) and 4B (side view). The accessory (400) can be a case for the mobile phone, a “shim” that can be positioned between the PTx and the PRx, or another intermediate device comprising the ferrite core (300). The ferrite core (300) can be positioned within the accessory (400), wherein the accessory is designed and dimensioned to properly position the core (300) relative to the PRx windings of the PRx device. For example, placing the phone within the case may align the ferrite core (300) with the power receiving winding (105) of the phone (104) such that the inner diameter of the ferrite core/ring (300) aligns with the outer diameter of the receiver winding (105) and the annular portion of the ferrite core/ring (300) shields the friendly metal of the phone (104) from the flux induced by the PTx winding (103) of the charging pad (102).

As illustrated in FIGS. 5A and 5B, 6A and 6B, and 7A and 7B, respectively, the case (500, 600, or 700) may also optionally include one or more mechanisms to assist the user in aligning the accessory/phone combination with the external charging device. However, by way of example, such an accessory, whether a case, a SIM, or otherwise, may also include one or more magnets that may serve to align the accessory/device combination with a wireless power transmitter and/or receiver device having complementary arranged magnets. This alignment may assist in aligning the respective coils of the devices as well as the ferrite core (300) with the PTx winding (103) and/or the PRx winding (105). In FIGS. 5A and 5B , the magnet ring (502) is depicted as being beneath the ferrite ring (300), or in other words, the ferrite ring (300) is positioned between the magnets and the device ( e.g. , a phone, not shown). As in the embodiment of FIGS. 4A and 4B , the ferrite ring (300) prevents flux from coupling from the transmitter to the “friendly metal” of the device, thereby reducing undesirable power losses and associated heating. Additionally, the magnets of the magnet ring (502) may be segmented to reduce losses. In this embodiment, the accessory may be mechanically positioned and secured to the device (according to various known techniques), and the magnets may be used to assist in attaching and aligning the device/accessory combination to a power transmitting device (e.g., a charging pad, not shown). Additionally, as mentioned above and described in more detail below, the ferrite ring (300) may also be segmented, in which case the magnet ring segments and the ferrite ring segments may be interspersed as illustrated below in connection with FIG. 10.

In FIGS. 6A and 6B , the magnet ring (502) is depicted as being over the ferrite ring (300), or in other words, the ferrite ring (300) is positioned between the magnets and the power transmitting device (e.g., a charging pad, not shown). As in the embodiments of FIGS. 4A and 4B and 5A and 5B , the ferrite ring (300) prevents flux from coupling from the transmitter to the “friendly metal” of the device, thereby reducing undesirable power losses and associated heating. Additionally, the magnets of the magnet ring (502) may be segmented to reduce losses. In this embodiment, an accessory (e.g., a case or shim) may be magnetically secured (and aligned) to the device (e.g., a phone), and the device/accessory combination may be freely positioned relative to the power transmitting device (e.g., a charging pad, not shown). As described above and in more detail below, the ferrite ring (300) may also be segmented, in which case the magnet ring segments and the ferrite ring segments may be interspersed as illustrated below in connection with FIG. 10.

In FIGS. 7A and 7B , the magnet ring (502) is shown as being substantially coplanar with the ferrite ring (300). Exact coplanarity is not required, and may not even be possible in a given embodiment, depending on the respective heights of the magnets and the ferrite core. As in the embodiments of FIGS. 4A and 4B , 5A and 5B , and 6A and 6B discussed above, the ferrite ring (300) prevents flux from coupling from the transmitter to the "friendly metal" of the device, thereby reducing undesirable power loss and associated heating. Additionally, the magnets of the magnet ring (502) may be segmented to reduce losses. In this embodiment, the magnets may be used to secure and position an accessory relative to the device and/or a power transmitting device (e.g., a charging pad).

As shown in FIGS. 7A and 7B , in FIG. 10 , the magnet ring (502) is shown as being substantially coplanar with the ferrite ring (300). As discussed above, exact coplanarity is not required, especially given the possibility of different respective heights of the magnets and ferrite core for the given embodiment. However, for packaging purposes, it may be helpful for the magnet components within the ring (502) and the ferrite components within the ring (300) to be arranged so that at least some of these components are coplanar to reduce the z-height of the resulting accessory. As in the embodiments of FIGS. 4A and 4B , 5A and 5B , 6A and 6B , and 7A and 7B discussed above, the ferrite ring (300) prevents flux from coupling from the transmitter to the "friendly metal" of the device, thereby reducing undesirable power loss and associated heating. Additionally, the magnets of the magnet ring (502) are segmented into segments ("M") to reduce losses and improve manufacturability. The ferrite ring (300) is similarly segmented into segments ("F") sandwiched between the magnet segments ("M"). As such, the magnets may be used to secure and position the accessory relative to the device and/or power transmitting device (e.g., a charging pad). The relative sizes of the magnet segments and the ferrite segments, both radially and circumferentially, may be adjusted as needed to provide sufficient engagement force between the accessory (1000) and the device (e.g., a phone) and/or power transmitter (by increasing the size of the magnets) and/or to increase the flux shielding/coupling effect (by increasing the size of the ferrite segments). In some embodiments, the relative positioning of the magnet ring segments and the ferrite ring segments may be such that the various segments are substantially collinear along the circumference of the respective rings. Depending on the specific dimensions of the ferrite ring segments and magnet ring segments, exact collinearity may not be required or provided, as a wide collinearity around the circumference may be adequate for some applications.

Figure 8 illustrates an alternative embodiment of a flux shielding/direction accessory (801) comprising a ferrite core (300). The accessory (801) may be a shim device configured to position and optionally secure to the PTx device (102) itself. (As noted above, the PTx device (102) may be, for example, a charging mat, a charging pad, or other suitable wireless/inductive charging device.) The accessory (801) may also include mechanical, adhesive, and/or magnetic features (802) for aligning and/or securing the intermediate device (801) to the PTx (102) and associated PTx winding (103). As described above, the core (300) should be dimensioned so as to suitably reduce unwanted flux coupling to the friendly metal of the PRx device (e.g., a mobile phone or other electronic device or accessory) and/or enhance flux coupling to the PRx winding (105) of the PRx device. As such, it will need to be positioned relative to the PTx winding (105) such that it intercepts and/or diverts flux that would normally couple to the friendly metal of the PRx device.

FIG. 9 illustrates additional details of embodiments (902, 904) of a flux shielding/direction accessory (801) (FIG. 8). In embodiments (902, 904), a PTx device (102) may include a plurality of transmit coils (103) arranged as DDQ coils. The accessory (902, 904) may be positioned between the PTx device (102) and a PRx device (104) ( e.g. , a mobile phone). The accessory (902, 904) may include a ferrite ring (300), which may be implemented as a ferrite frame (300) surrounding the top/Q coil (103) of the PTx device (102). As a result, the affinity metal of the PRx device (104) is effectively shielded from the flux induced by the coil (103). Similarly, the accessory (904) may include a ferrite frame covering all or substantially all of the transmit area of the PTx device (904). In such an embodiment, additional ferrite bars (910) may be provided near specific coils as needed to provide the necessary level of shielding/flux diversion. Optional tabs (912) within the ferrite ring/frame (300) may also be used for similar effect.

The foregoing describes exemplary embodiments of accessories for wireless power transfer systems that provide improved coupling between a wireless power transmitter (PTx) device and a wireless power receiver (PRx) device. Such systems may be used in a variety of applications, but may be particularly advantageous when used with wireless charging devices (e.g., charging mats, pads, stands, etc.) configured for use with different devices, and with electronic devices, such as mobile computing devices (e.g., laptop computers, tablet computers, smartphones, etc.) and their accessories (e.g., wireless earbuds, styli, and other input devices, etc.). While numerous specific features and various embodiments have been described, it should be understood that the various features and embodiments may be combined in various permutations in particular implementations, unless otherwise stated as mutually exclusive. Accordingly, the various embodiments described above are provided by way of example only and should not be construed as limiting the scope of the present disclosure. Various modifications and changes may be made to the principles and embodiments of the present disclosure without departing from the scope of the claims.

The techniques set forth and claimed herein clearly advance the state of the art and are therefore directed to and applied to tangible objects and concrete examples of practical nature, rather than abstract, intangible, or purely theoretical. Additionally, to the extent that any claims appended to the end of this specification include one or more elements designated as “means for performing [the function]…” or “steps for performing [the function]…”, it is intended that such elements be construed under 35 U.S.C. 112(f). However, for any claims that include elements designated in any other manner, it is intended that such elements will not be construed under 35 U.S.C. 112(f).

Claims (15)

A case for an electronic device, configured to improve wireless power transfer efficiency between the electronic device and a wireless charger, wherein the case comprises:
One or more alignment fixtures for aligning or securing the case to the electronic device; and
A case for an electronic device, comprising one or more alignment magnets for aligning and securing an accessory to one or more complementarily arranged alignment magnets within the wireless charger. A case for an electronic device, wherein the one or more magnets form a ring in the first paragraph. A case for an electronic device, wherein the one or more magnets are segmented in the second paragraph. In the first paragraph, a core having magnetic properties, dimensions, and positions is further included, wherein the core is:
Reducing flux coupling from the wireless charging winding of the wireless charger to the friendly metal of the electronic device;
A case for an electronic device, which improves flux coupling from the wireless charging coil of the wireless charger to the wireless charging coil of the electronic device. A case for an electronic device, wherein the core is made of ferrite or other material having suitable magnetic properties. A case for an electronic device, wherein the core is made of sintered ferrite in the fifth paragraph. A case for an electronic device, wherein the core is made of nanocrystalline sheets in the fifth paragraph. A case for an electronic device, wherein the wireless charging coil of the electronic device and the wireless charging coil of the wireless charger are dimensionally mismatched in the fourth paragraph. A case for an electronic device, wherein in claim 8, the dimensional mismatch includes the wireless charging winding of the charger being larger than the wireless charging winding of the electronic device, and the core defines an aperture corresponding to an external dimension of the wireless charging winding of the electronic device. A case for an electronic device, wherein the core has external dimensions selected to intercept sufficient flux to reduce flux coupling to the affinity metal of the electronic device. A case for an electronic device, wherein the aperture has an inner diameter corresponding to an outer diameter of the wireless charging coil of the wireless charger. A case for an electronic device, wherein the core is a ferrite ring dimensioned to shield a friendly metal of the electronic device from a flux induced by at least one wireless charging winding of the wireless power transmitter. A case for an electronic device, wherein the ferrite ring is segmented in the 12th paragraph. A case for an electronic device, wherein the ferrite ring comprises one or more tabs sized and dimensioned to be positioned near one or more wireless charging windings of the wireless power transmitter to provide at least one of shielding or flux redirection. A case for an electronic device, wherein the core further comprises additional ferrite bars sized and dimensioned to be positioned near one or more of the wireless charging windings of the wireless power transmitter to provide at least one of shielding or flux redirection.